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Studies on the Relationship between Defense Substance and Pathogen of Ring Rot Disease on ’Ya’ Pear

Author: ZhaoXiaoFang
Tutor: ZhuMeiYun；WangGuiZuo
School: Henan Agricultural University
Course: Of Food Science
Keywords: pear fruit ring rot disease defense substance pathogen interaction relationship
CLC: TS255.1
Type: Master's thesis
Year: 2008
Downloads: 73
Quote: 3
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Abstract

Pear ring rot caused by Botryosphaeria erengriana f.sp.piricola is a main disease for pear.Because pathogenic germs can infect the host pear latently at growth stage,and induce rot during the post-harvest period.In order to control this kind of disease,it is necessary to know the mechanisms,how the pathogen developing in pear fruit and cause the decay,and how the fruit resist the disease development.Up to now,the developing mechanisms of ring rot have been ascertained basically,but the defensive mechanisms of fruit against pathogen are not distinct.In order to discuss the defensive ability of pear fruit against pathogen,the change of the variety and content of resistant substance including organic acids,phenolics and enzymes in Ya’ pear fruit inoculated with Botryosphaeria berengriana f.sp.piricola and sound pear fruit in growth and storage periods were studied,which can provide theoretic basis for resistance of pear against ring rot and also can offer feasible way to control the post-harvest disease.1.The main organic acids including Malic acid,Citric acid and Shikimic acid were found in premature pear fruit,and the content of all the organic acids and total acid decreased with the ripeness course of fruit.In the prophase of storage,the content of main organic acids increased,then all downtrend along with the storing extend.The content of Malic acid and Citric acid in rotten pulp was higher than that of edge of healthy pulp,while Quinic acid and Tartaric acid were lower than the latter.The new organic acids - Lactic acid measured from rot section and the edge of health,and Succinic acid also found at the edge of health.2.The HPLC results of different section of pear fruit infected by ring rot disease showed that the content of Chlorogenic acid,Gallic acid and Caffeic acid were higher than that of sound fruit, also Catehin content of rot section was markedly increased.All suggested that the increase of phenolics is closed relate to the ring rot disease development.The main defense phenolics of pear fruit during growth were Chlorogenic acid,Gallic acid and Tannic acid.The three phenolics content declined sharply,and the content of Catehin,Rutin and Coumaric acid were piled up in premature fruit,which are related to the defense of phenolic.The content of Chlorogenic acid,Gallic acid in pear during storage were decreased and disappeared accompany with the physiological functions declined.3.The determination results of several enzymes activity show that the PPO activity of pear fruit in 72hs inoculated by Botryosphaeria erengriana were higher than sound fruit,which suggest PPO is related to forepart resistant of fruit against ring rot disease;Compared with sound fruit,PAL activities of pear in 120hs and the activities of POD,Chitinase andβ-1,3-glucanase of inoculated fruits of pear in 72hs were also markedly increased after inoculated.The four enzymes above were related to the whole time defense after it inoculated.Also the CAT and SOD activities of pear fruit were also increased after being inoculated by ring rot disease.The main defense enzymes with high activity at the young stage of pear fruit were PPO、POD、CAT and PAL.the whole activities of these enzyme at rapid growing stage decreased sharply,the main defense enzymes with high activity at premature stage of fruit were SOD、PAL、Chitinase andβ-1,3-glucanase.The activities of these enzymes all declined during storage.4.The influence of isolated resistant substance with different verity and content to the pathogen were studied,and the result showed that the concentration higher than 50 mg/100g Malic acid,150 mg/100g Citric acid,80 mg/100g Lactic acid and 10 mg/100g Succinic acid can inhibit the hypal growing,higher than 5mg/100g Quinic acid and 20mg/100g Fumaric acid can improve it growing.The pathogen conlony growth was inhibited by higher concentration of 10mg/100g gallic acid,1mg/100g chlorgenic acid,5mg/100g Tannic acid 0.05mg/100g coumaric acid and lower concentration of 1mg/100g Rutin in PSA culture medium.Higher activities of PPO/POD、PAL and CHT/β-1,3-GLU also restrain pathogen growing,which were consistent with the enzymes activities change in pear fruit inoculated by Botryosphaeria erengriana.To sum up,the thesis found that the content(activity)of resistant substance such as organic acids,phenolics and enzymes of pear fruit infected by ring rot disease were improved,and the new resistant component can be abduced by pathogeny fungus.Isolated organic acids,phenolics and enzymes with different verity and content could affect pathogen growing differently.Different verity and content defense substance in pear fruit during growth and storage changed in phase.

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